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Mechanical properties of F82H plates with different thicknesses
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Mechanical properties of F82H plates with different thicknesses Hideo Sakasegawa ∗ , Hiroyasu Tanigawa Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212, Japan
h i g h l i g h t s • • • •
Mass effect, homogeneity, and anisotropy in mechanical properties were studied. Thickness dependence of tensile property was not observed. Thickness dependence of Charpy impact property was observed. Appropriate mechanical properties were obtained using an electric furnace.
a r t i c l e
i n f o
Article history: Received 4 August 2015 Received in revised form 12 October 2015 Accepted 15 October 2015 Available online xxx Keywords: DEMO fusion reactor Blanket Reduced activation ferritic/martensitic steel Mechanical property Homogeneity Anisotropy
a b s t r a c t Fusion DEMO reactor requires over 11,000 tons of reduced activation ferritic/martensitic steel and it is indispensable to develop the manufacturing technology for producing large-scale components of DEMO blanket with appropriate mechanical properties. This is because mechanical properties are generally degraded with increasing production volume. In this work, we focused mechanical properties of F82H–BA12 heat which was melted in a 20 tons electric arc furnace. Plates with difference thicknesses from 18 to 100 mmt were made from its ingot through forging and hot-rolling followed by heat treatments. Tensile and Charpy impact tests were then performed on plates focusing on their homogeneity and anisotropy. From the result, their homogeneity and anisotropy were not significant. No obvious differences were observed in tensile properties between the plates with different thicknesses. However, Charpy impact property changed with increasing plate thickness, i.e. the ductile brittle transition temperature of a 100 mmt thick plate was higher than that of the other thinner plates. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Fusion DEMO reactor requires over 11,000 tons of reduced activation ferritic/martensitic steel (RAFM) [1]. Electric furnaces are generally used to commercially produce such large-scale volume of steels, because the melting volume of vacuum induction furnaces, which have been used to prepare laboratory-scale RAFMs, is limited less than few tons. In addition, electrolytic iron, which has been used to prepare laboratory-scale RAFMs, cannot be used to meet the requirement of over 11,000 tons of RAFM, because its production volume is also limited. Against such background, F82H–BA12 heat was melted in a 20 tons electric arc furnace using a blast furnace iron as its raw material of iron through the Broader Approach activity in Japan. Its fundamental mechanical properties such as tensile property and Charpy impact property were then studied and obvious degradations were not observed in these mechanical properties, compared
∗ Corresponding author. E-mail address: [email protected] (H. Sakasegawa).
to the former heats [2]. However, there still remain issues of homogeneity, anisotropy, and mass effect for producing large-scale components of DEMO blanket. This is because mechanical properties are generally affected and changed with increasing production volume. It is important to develop manufacturing technologies specialized to producing large-scale components of DEMO blanket with appropriate mechanical properties. In this work, we studied fundamental mechanical properties such as tensile property and Charpy impact property of F82H–BA12 plates with different thicknesses from 18 to 100 mmt and focused homogeneity, anisotropy, and mass effect to contribute to the development of manufacturing technologies for producing largescale components made of F82H. 2. Experimental 2.1. Material F82H–BA12 heat was melted using a 20 tons electric arc furnace at Daido Steel Co., Ltd. Refining, casting, electroslag remelting, and forging were then performed and four slabs
http://dx.doi.org/10.1016/j.fusengdes.2015.10.017 0920-3796/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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2 Table 1 Chemical composition of F82H heats (wt%). Element
C Si Mn P S Cr W V Ta B Ti O N Total Al Sol. Al Fe
Heat IEA
BA07
BA10
BA11 FWG
BA11 STG
BA12
0.09 0.07–0.11 0.10–0.16 0.002–0.003 0.001–0.002 7.64–7.89 1.95–2.00 0.16–0.19 0.02–0.04 0.0002 0.004–0.01 – 0.005–0.008 – 0.001–0.003 Bal.
0.088–0.090 0.16–0.17 0.45–0.46 0.008–0.009 0.002–0.003 7.97–8.02 1.88 0.19 0.03–0.04 0.002 <0.003 0.001–0.002 0.015–0.019 – 0.007 Bal.
0.093 0.11 0.45 0.004 0.001 7.95 1.87 0.21 0.03 0.001 0.001 0.0015 0.0030 – 0.001 Bal.
0.084–0.085 0.16 0.42 0.009–0.010 <0.001 7.94 1.87 0.19 0.10–0.11 <0.0001 <0.001 0.0014–0.0015 0.008 0.007–0.009 0.006–0.008 Bal.
0.10–0.104 0.11–0.15 0.47 <0.005–0.005 0.0010–0.001 7.94–7.99 1.83–1.91 0.20 0.037–0.05 0.0003 <0.001–<0.002 0.0020–0.0022 0.01–0.0128 0.02–0.034 0.014–0.031 Bal.
0.099 0.10 0.45 0.011 <0.0005 7.88 1.78 0.19 0.093 0.0040 <0.001 0.0012 0.0098 0.022 0.022 Bal.
Sol., solution, Bal, balance.
(270t mm × 500w mm × 2200l mm) and two billets (210 mm × 2600 mm) were fabricated. The chemical composition of BA12 heat was given in Table 1 in addition to former heats: IEA, BA07, BA10, BA11 FWG (First Wall Grade), and BA11 STG (Standard Grade) heats as a reference, which were melted using vacuum induction furnaces less than 5 tons. Compared to other heats, BA12 heat has a higher tantalum content to obtain a better resistance to irradiation embrittlement and a reduced susceptibility to a deviation of heat treatment condition [3]. Plates with different thicknesses of 18, 25, 55, and 100 mmt were made through forging and hot-rolling from slabs and then heat-treated under the condition of normalizing at 1040 ◦ C for 40 min and tempering at 750 ◦ C for 60 min, which were followed by air cooling. The thicknesses of plate were decided considering the latest design of DEMO blanket and its manufacturing process such as machining, bending, and joining to fabricate the blanket structure.
Fig. 1. Tensile property of BA12 heat plate.
2.2. Tensile and Charpy impact tests Tensile and Charpy impact tests were performed in conformity to JIS Z2241 and JIS Z2242, respectively. These specimens were machined from the 1/2 and/or 1/4 positions in thickness direction, and the longitudinal direction of specimen is parallel or perpendicular to the hot-rolling direction in order to study homogeneity and anisotropy in these mechanical properties. High-temperature tensile test was additionally performed from 20 to 600 ◦ C complying with JIS Z0567 to fundamentally study a high temperature mechanical property of BA12 heat. These test conditions meet the requirement in the guideline of new material registration of JSME (The Japan Society of Mechanical Engineers). This is because it is indispensable to standardize and register F82H for the actual application as a material of DEMO blanket. The obtained results from these tests were compared to those of IEA, BA07, BA10, BA11 FWG and BA11 STG heats [4]. 3. Results and discussion 3.1. Tensile property Fig. 1 shows the result of tensile test on BA12 heat plates with 18, 25, 55, and 100 mmt . YS (yield strength), UTS (ultimate tensile strength), and TE (total elongation) were given in the figure. The position in thickness (1/2t and 1/4t) and the direction (L: longitudinal and T: transversal) were also shown. “L” means that the specimen was machined parallel to the hot-rolled direction and
Fig. 2. Temperature dependence of tensile property of BA12 heat plate (18 mmt , L).
“T” means that the specimen was machined perpendicular to the hot-rolled direction. In this figure, YS and UTS slightly decreased with increasing thickness, but this change was not significant. No obvious differences were observed in their homogeneity and anisotropy. Mass effect was hardly observed in the tensile property of BA12 heat plates. In Fig. 2, YS, UTS, and TE obtained from the high-temperature tensile test were given. The test was performed on the specimens machined from the 18 mmt plate of BA12 heat parallel to the
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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Fig. 4. Grain of F82H BA12 heat. Fig. 3. Charpy impact property of BA12 heat plate.
hot-rolled direction. The results were compared to those of IEA and BA07 heats which were melted using vacuum induction furnaces about 5 tons. No significant differences were observed and comparable tensile property was obtained in BA12 heat melted in a 20 tons electric arc furnace. In addition, these obtained results were comparable to those of Mod. 9Cr-1Mo steel (Grade 91) in ASME (The American Society of Mechanical Engineers) and met its specified requirements, YS: >414 MPa and UTS: 585–760 MPa at room temperature [5]. 3.2. Charpy impact property Fig. 3 shows the result of Charpy impact test result. Fig. 3(a) shows DBTT (Ductile Brittle Transition Temperature) and (b) shows absorbed energy at 0 ◦ C. The position in thickness (1/2t and 1/4t) and the direction (L and T) were also given, as already explained in Fig. 1. No significant differences were observed in their homogeneity and anisotropy in Fig. 3(a) and (b), but with increasing thickness, DBTT clearly increased and absorbed energy at 0 ◦ C decreased. The reason why Charpy impact property was degraded depending on thickness can be interpreted by grain size. Fig. 4(a) shows thickness dependence of grain size. In this figure, the position in thickness (1/2t and 1/4t) and the direction (L and T) were also given. No significant differences were observed in their homogeneity and anisotropy, but grain size increased with increasing of thickness. In particular, as shown in Fig. 4(b), some largely coarsened grains larger than 100 m appeared in the 100 mmt plate. Grain size is
strongly correlated with rolling ratio. The higher is the rolling ratio, the finer is the prior austenite grain size. It is well known that refining grain size is very effective to improve material toughness. The 100 mmt plate had the lowest hot-rolling ratio and the largest grain size which possibly resulted in the highest DBTT and the lowest energy at 0 ◦ C. However, the DBTT of the 100 mmt plate was still lower than 0 ◦ C and the value of absorbed energy at 0 ◦ C was much higher than 40 J which is the required value for martensitic steels in ESPN (Équipements sous Pression Nucléaires: French order concerning nuclear pressure equipment) [6]. F82H–BA12 heat plates had an approval material toughness as one of the martensitic steels. 3.3. Thickness dependence of tensile and Charpy impact properties including other heats Fig. 5(a) and (b) shows thickness dependence of tensile property and Charpy impact property, respectively. These figures were obtained summarizing the past data of former F82H heats as shown in Table 1 and this data covered plate thicknesses ranging from 15 to 110 mmt . In actual fabrication of DEMO blanket, plates should be used within this range, based on the latest design [1]. As for tensile property, plates thicker than 90 mmt showed slightly higher YS and UTS, but no significant change in TE was observed depending on thickness, as given in Fig. 5(a). These obtained values met the requirements of Mod. 9Cr-1Mo steel specified in ASME and the heats of F82H showed the tensile property comparable to Mod. 9Cr-1Mo steel [5]. As for Charpy impact property, thickness dependence was observed, as given in Fig. 5(b). Absorbed energy at 0 ◦ C tends to
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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4. Summary In this work, we studied tensile and Charpy impact property of F82H–BA12 heat plates with different thicknesses from 18 to 100 mmt and focused homogeneity and anisotropy in these mechanical properties. No obvious differences were observed in tensile property between the plates with different thicknesses. Their homogeneity and anisotropy were not significant. However, Charpy impact property changed. With increasing thickness, DBTT increased and absorbed energy at 0 ◦ C decreased, though their homogeneity is uniform and anisotropy is not significant. This thickness dependence possibly resulted from hot-rolling ratio, which strongly affects the refinement of grain size. The obtained mechanical properties of BA12 heat were then summarized and compared to those of past F82H heats. Including other F82H heats, similar results were obtained. Significant thickness dependence of tensile property was not observed and the tensile property of F82H was comparable to that of Mod. 9Cr-1Mo steel specified in ASME. It is important to continue the activity to obtain, accumulate, and study mechanical properties of F82H for fabricating large components of DEMO blanket. In particular, the standardization of F82H is necessary basing on this activity, because ITER and DEMO have to be constructed in conformity to codes and standards such as ASME, RCC-MRx, and JSME. Acknowledgements This paper has been prepared as an account of work assigned to the Japanese Implementing Agency under the Procurement Number IFERC-T3PA03-JA within the “Broader Approach Agreement” between the Government of Japan and the European Atomic Energy Community. Fig. 5. Thickness dependence of tensile and Charpy impact property.
decrease. However, the highest DBTT was still lower than 0 ◦ C and the lowest absorbed energy at 0 ◦ C was higher than 40 J, which meets ESPN requirement for martensitic steels [6]. The heats of F82H showed an approval material toughness as a martensitic steel. This thickness dependence is not possibly caused by mass effect during heat treatments, but dominantly caused by hot-rolling ratio. This is because thicker plates tend to have coarser grains and a mixed grain structure, which leads to degradation in material toughness, as already explained in Fig. 4(b). However, it is indispensable to continue obtain and accumulate mechanical properties of F82H with focusing on mass effect for fabricating the DEMO blanket. This is because mass effect could generally cause unexpected changes in mechanical properties in mass production.
References [1] H. Tanigawa, et al., Radiological assessment of the limits and potential of reduced activation ferritic/martensitic steels, Fus. Eng. Des. 89 (2014) 1573–1578. [2] H. Sakasegawa, H. Tanigawa, S. Kano, H. Abe, Material properties of the F82H melted in an electric arc furnace, Fus. Eng. Des., http://dx.doi.org/10.1016/j. fusengdes.2015.06.103 (in press). Corrected proof, available online 15 July 2015. [3] K. Shiba, et al., Development of the toughness-improved reduced-activation F82H steel for DEMO roughness-improved reduced-activation F82H steel for DEMO reactor, Fus. Sci. Technol. 62 (2012) 145–149. [4] H. Sakasegawa, et al., Effect of potential factors in manufacturing process on mechanical properties of F82H, Fus. Eng. Des. 89 (2014) 1684–1687. [5] ASME/BPVC. SEC II-A-1, Section II. A Ferrous Material Specifications (Beginning to SA-450) Materials, 697–702. [6] Order 2005 December 12 for nuclear pressurized equipment (ESPN) FR (24FF4V), 12.
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
ARTICLE IN PRESS
FUSION-8295; No. of Pages 4
Fusion Engineering and Design xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Mechanical properties of F82H plates with different thicknesses Hideo Sakasegawa ∗ , Hiroyasu Tanigawa Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212, Japan
h i g h l i g h t s • • • •
Mass effect, homogeneity, and anisotropy in mechanical properties were studied. Thickness dependence of tensile property was not observed. Thickness dependence of Charpy impact property was observed. Appropriate mechanical properties were obtained using an electric furnace.
a r t i c l e
i n f o
Article history: Received 4 August 2015 Received in revised form 12 October 2015 Accepted 15 October 2015 Available online xxx Keywords: DEMO fusion reactor Blanket Reduced activation ferritic/martensitic steel Mechanical property Homogeneity Anisotropy
a b s t r a c t Fusion DEMO reactor requires over 11,000 tons of reduced activation ferritic/martensitic steel and it is indispensable to develop the manufacturing technology for producing large-scale components of DEMO blanket with appropriate mechanical properties. This is because mechanical properties are generally degraded with increasing production volume. In this work, we focused mechanical properties of F82H–BA12 heat which was melted in a 20 tons electric arc furnace. Plates with difference thicknesses from 18 to 100 mmt were made from its ingot through forging and hot-rolling followed by heat treatments. Tensile and Charpy impact tests were then performed on plates focusing on their homogeneity and anisotropy. From the result, their homogeneity and anisotropy were not significant. No obvious differences were observed in tensile properties between the plates with different thicknesses. However, Charpy impact property changed with increasing plate thickness, i.e. the ductile brittle transition temperature of a 100 mmt thick plate was higher than that of the other thinner plates. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Fusion DEMO reactor requires over 11,000 tons of reduced activation ferritic/martensitic steel (RAFM) [1]. Electric furnaces are generally used to commercially produce such large-scale volume of steels, because the melting volume of vacuum induction furnaces, which have been used to prepare laboratory-scale RAFMs, is limited less than few tons. In addition, electrolytic iron, which has been used to prepare laboratory-scale RAFMs, cannot be used to meet the requirement of over 11,000 tons of RAFM, because its production volume is also limited. Against such background, F82H–BA12 heat was melted in a 20 tons electric arc furnace using a blast furnace iron as its raw material of iron through the Broader Approach activity in Japan. Its fundamental mechanical properties such as tensile property and Charpy impact property were then studied and obvious degradations were not observed in these mechanical properties, compared
∗ Corresponding author. E-mail address: [email protected] (H. Sakasegawa).
to the former heats [2]. However, there still remain issues of homogeneity, anisotropy, and mass effect for producing large-scale components of DEMO blanket. This is because mechanical properties are generally affected and changed with increasing production volume. It is important to develop manufacturing technologies specialized to producing large-scale components of DEMO blanket with appropriate mechanical properties. In this work, we studied fundamental mechanical properties such as tensile property and Charpy impact property of F82H–BA12 plates with different thicknesses from 18 to 100 mmt and focused homogeneity, anisotropy, and mass effect to contribute to the development of manufacturing technologies for producing largescale components made of F82H. 2. Experimental 2.1. Material F82H–BA12 heat was melted using a 20 tons electric arc furnace at Daido Steel Co., Ltd. Refining, casting, electroslag remelting, and forging were then performed and four slabs
http://dx.doi.org/10.1016/j.fusengdes.2015.10.017 0920-3796/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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ARTICLE IN PRESS H. Sakasegawa, H. Tanigawa / Fusion Engineering and Design xxx (2015) xxx–xxx
2 Table 1 Chemical composition of F82H heats (wt%). Element
C Si Mn P S Cr W V Ta B Ti O N Total Al Sol. Al Fe
Heat IEA
BA07
BA10
BA11 FWG
BA11 STG
BA12
0.09 0.07–0.11 0.10–0.16 0.002–0.003 0.001–0.002 7.64–7.89 1.95–2.00 0.16–0.19 0.02–0.04 0.0002 0.004–0.01 – 0.005–0.008 – 0.001–0.003 Bal.
0.088–0.090 0.16–0.17 0.45–0.46 0.008–0.009 0.002–0.003 7.97–8.02 1.88 0.19 0.03–0.04 0.002 <0.003 0.001–0.002 0.015–0.019 – 0.007 Bal.
0.093 0.11 0.45 0.004 0.001 7.95 1.87 0.21 0.03 0.001 0.001 0.0015 0.0030 – 0.001 Bal.
0.084–0.085 0.16 0.42 0.009–0.010 <0.001 7.94 1.87 0.19 0.10–0.11 <0.0001 <0.001 0.0014–0.0015 0.008 0.007–0.009 0.006–0.008 Bal.
0.10–0.104 0.11–0.15 0.47 <0.005–0.005 0.0010–0.001 7.94–7.99 1.83–1.91 0.20 0.037–0.05 0.0003 <0.001–<0.002 0.0020–0.0022 0.01–0.0128 0.02–0.034 0.014–0.031 Bal.
0.099 0.10 0.45 0.011 <0.0005 7.88 1.78 0.19 0.093 0.0040 <0.001 0.0012 0.0098 0.022 0.022 Bal.
Sol., solution, Bal, balance.
(270t mm × 500w mm × 2200l mm) and two billets (210 mm × 2600 mm) were fabricated. The chemical composition of BA12 heat was given in Table 1 in addition to former heats: IEA, BA07, BA10, BA11 FWG (First Wall Grade), and BA11 STG (Standard Grade) heats as a reference, which were melted using vacuum induction furnaces less than 5 tons. Compared to other heats, BA12 heat has a higher tantalum content to obtain a better resistance to irradiation embrittlement and a reduced susceptibility to a deviation of heat treatment condition [3]. Plates with different thicknesses of 18, 25, 55, and 100 mmt were made through forging and hot-rolling from slabs and then heat-treated under the condition of normalizing at 1040 ◦ C for 40 min and tempering at 750 ◦ C for 60 min, which were followed by air cooling. The thicknesses of plate were decided considering the latest design of DEMO blanket and its manufacturing process such as machining, bending, and joining to fabricate the blanket structure.
Fig. 1. Tensile property of BA12 heat plate.
2.2. Tensile and Charpy impact tests Tensile and Charpy impact tests were performed in conformity to JIS Z2241 and JIS Z2242, respectively. These specimens were machined from the 1/2 and/or 1/4 positions in thickness direction, and the longitudinal direction of specimen is parallel or perpendicular to the hot-rolling direction in order to study homogeneity and anisotropy in these mechanical properties. High-temperature tensile test was additionally performed from 20 to 600 ◦ C complying with JIS Z0567 to fundamentally study a high temperature mechanical property of BA12 heat. These test conditions meet the requirement in the guideline of new material registration of JSME (The Japan Society of Mechanical Engineers). This is because it is indispensable to standardize and register F82H for the actual application as a material of DEMO blanket. The obtained results from these tests were compared to those of IEA, BA07, BA10, BA11 FWG and BA11 STG heats [4]. 3. Results and discussion 3.1. Tensile property Fig. 1 shows the result of tensile test on BA12 heat plates with 18, 25, 55, and 100 mmt . YS (yield strength), UTS (ultimate tensile strength), and TE (total elongation) were given in the figure. The position in thickness (1/2t and 1/4t) and the direction (L: longitudinal and T: transversal) were also shown. “L” means that the specimen was machined parallel to the hot-rolled direction and
Fig. 2. Temperature dependence of tensile property of BA12 heat plate (18 mmt , L).
“T” means that the specimen was machined perpendicular to the hot-rolled direction. In this figure, YS and UTS slightly decreased with increasing thickness, but this change was not significant. No obvious differences were observed in their homogeneity and anisotropy. Mass effect was hardly observed in the tensile property of BA12 heat plates. In Fig. 2, YS, UTS, and TE obtained from the high-temperature tensile test were given. The test was performed on the specimens machined from the 18 mmt plate of BA12 heat parallel to the
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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Fig. 4. Grain of F82H BA12 heat. Fig. 3. Charpy impact property of BA12 heat plate.
hot-rolled direction. The results were compared to those of IEA and BA07 heats which were melted using vacuum induction furnaces about 5 tons. No significant differences were observed and comparable tensile property was obtained in BA12 heat melted in a 20 tons electric arc furnace. In addition, these obtained results were comparable to those of Mod. 9Cr-1Mo steel (Grade 91) in ASME (The American Society of Mechanical Engineers) and met its specified requirements, YS: >414 MPa and UTS: 585–760 MPa at room temperature [5]. 3.2. Charpy impact property Fig. 3 shows the result of Charpy impact test result. Fig. 3(a) shows DBTT (Ductile Brittle Transition Temperature) and (b) shows absorbed energy at 0 ◦ C. The position in thickness (1/2t and 1/4t) and the direction (L and T) were also given, as already explained in Fig. 1. No significant differences were observed in their homogeneity and anisotropy in Fig. 3(a) and (b), but with increasing thickness, DBTT clearly increased and absorbed energy at 0 ◦ C decreased. The reason why Charpy impact property was degraded depending on thickness can be interpreted by grain size. Fig. 4(a) shows thickness dependence of grain size. In this figure, the position in thickness (1/2t and 1/4t) and the direction (L and T) were also given. No significant differences were observed in their homogeneity and anisotropy, but grain size increased with increasing of thickness. In particular, as shown in Fig. 4(b), some largely coarsened grains larger than 100 m appeared in the 100 mmt plate. Grain size is
strongly correlated with rolling ratio. The higher is the rolling ratio, the finer is the prior austenite grain size. It is well known that refining grain size is very effective to improve material toughness. The 100 mmt plate had the lowest hot-rolling ratio and the largest grain size which possibly resulted in the highest DBTT and the lowest energy at 0 ◦ C. However, the DBTT of the 100 mmt plate was still lower than 0 ◦ C and the value of absorbed energy at 0 ◦ C was much higher than 40 J which is the required value for martensitic steels in ESPN (Équipements sous Pression Nucléaires: French order concerning nuclear pressure equipment) [6]. F82H–BA12 heat plates had an approval material toughness as one of the martensitic steels. 3.3. Thickness dependence of tensile and Charpy impact properties including other heats Fig. 5(a) and (b) shows thickness dependence of tensile property and Charpy impact property, respectively. These figures were obtained summarizing the past data of former F82H heats as shown in Table 1 and this data covered plate thicknesses ranging from 15 to 110 mmt . In actual fabrication of DEMO blanket, plates should be used within this range, based on the latest design [1]. As for tensile property, plates thicker than 90 mmt showed slightly higher YS and UTS, but no significant change in TE was observed depending on thickness, as given in Fig. 5(a). These obtained values met the requirements of Mod. 9Cr-1Mo steel specified in ASME and the heats of F82H showed the tensile property comparable to Mod. 9Cr-1Mo steel [5]. As for Charpy impact property, thickness dependence was observed, as given in Fig. 5(b). Absorbed energy at 0 ◦ C tends to
Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017
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4. Summary In this work, we studied tensile and Charpy impact property of F82H–BA12 heat plates with different thicknesses from 18 to 100 mmt and focused homogeneity and anisotropy in these mechanical properties. No obvious differences were observed in tensile property between the plates with different thicknesses. Their homogeneity and anisotropy were not significant. However, Charpy impact property changed. With increasing thickness, DBTT increased and absorbed energy at 0 ◦ C decreased, though their homogeneity is uniform and anisotropy is not significant. This thickness dependence possibly resulted from hot-rolling ratio, which strongly affects the refinement of grain size. The obtained mechanical properties of BA12 heat were then summarized and compared to those of past F82H heats. Including other F82H heats, similar results were obtained. Significant thickness dependence of tensile property was not observed and the tensile property of F82H was comparable to that of Mod. 9Cr-1Mo steel specified in ASME. It is important to continue the activity to obtain, accumulate, and study mechanical properties of F82H for fabricating large components of DEMO blanket. In particular, the standardization of F82H is necessary basing on this activity, because ITER and DEMO have to be constructed in conformity to codes and standards such as ASME, RCC-MRx, and JSME. Acknowledgements This paper has been prepared as an account of work assigned to the Japanese Implementing Agency under the Procurement Number IFERC-T3PA03-JA within the “Broader Approach Agreement” between the Government of Japan and the European Atomic Energy Community. Fig. 5. Thickness dependence of tensile and Charpy impact property.
decrease. However, the highest DBTT was still lower than 0 ◦ C and the lowest absorbed energy at 0 ◦ C was higher than 40 J, which meets ESPN requirement for martensitic steels [6]. The heats of F82H showed an approval material toughness as a martensitic steel. This thickness dependence is not possibly caused by mass effect during heat treatments, but dominantly caused by hot-rolling ratio. This is because thicker plates tend to have coarser grains and a mixed grain structure, which leads to degradation in material toughness, as already explained in Fig. 4(b). However, it is indispensable to continue obtain and accumulate mechanical properties of F82H with focusing on mass effect for fabricating the DEMO blanket. This is because mass effect could generally cause unexpected changes in mechanical properties in mass production.
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Please cite this article in press as: H. Sakasegawa, H. Tanigawa, Mechanical properties of F82H plates with different thicknesses, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.10.017